Selective Cytotoxicity of Some Plant Extracts Against Hepatocellular Carcinoma Cells but Not Mesenchymal Stem Cells: A Pilot Screening

Introduction: Medicinal plants have been used for disease treatment throughout history, especially in Asia. Vietnam is a tropical country which possesses forests with a diversity of plants; among the plants, many have been historically used as alternative therapies for various disease treatments. In this study we aimed to evaluate the selective cytotoxicity of some plant extracts (collected from Vietnamese forests) against hepatocellular carcinoma cells HepG2, compared to adipose tissue-derived mesenchymal stem cells (ADSCs).

Methods: In this study, we collected nine plants and produced nine extracts from them; these included whole stem of Buchanania lucida, whole stem of Dipterocarpus turbinatus, Hopea recopei, whole stem of Shorea thorelii, bark of Shorea thorelii stem, bark of Dipterocarpus turbinatus stem, whole stem of Dipterocarpus costatus, bark of Dipterocarpus costatus stem, and rhizome of Boesenbergia pandurata. The cytotoxicity of these extracts on hepatocellular carcinoma cells and mesenchymal stem cells were determined based on IC₅₀ values calculated using Alamar Blue assay. Based on these IC₅₀ values, the side effect index (SEI) of extracts was determined. Only the extracts with low SEI were used in further assays to determine the apoptotic status of both hepatocellular carcinoma cells and mesenchymal stem cells via caspase 3/7 induction assay, nuclei disintegration (using Hoechst 33342 staining), and Annexin V staining assay.

Results: The results showed that B. pandurata extract had strong cytotoxicity toward HepG2 cells with lowest side index on mesenchymal stem cells (IC₅₀ on HepG2 of 222 ± 27.82 (μg/ml) but IC₅₀ on ADSCs of 382 ± 16.19 (μg/ml)). Nuclear staining showed that B. pandurata extract could induce disintegration of cell nuclei at the concentration of 400 μg/ml. After 3 h of incubation with B. pandurata extract at the concentration of 200 μg/ml, the BP extract induced caspase 3/7 activation in HepG2 cells, but not in mesenchymal stem cells. Annexin V staining showed that the BP extract induced apoptosis in HepG2 cells in a dose-dependent manner.

Conclusion: This study revealed that selective cytotoxicity of some extracts on cancer cells could be determined based on their IC₅₀ values on cancer cells and on mesenchymal stem cells. B. pandurata extract displayed the lowest side effect index on mesenchymal stem cells and successfully induced apoptosis in hepatocellular carcinoma cells HepG2 via activation of caspase 3/7.

Keywords: Adipose tissue-derived stem cell; Apoptosis; Boesenbergia pandurata extract; HepG2; Selective cytotoxicity.